A plan to "terraform" a planet to improve its habitability by human beings.

This is an early reference to the idea; see the discussion below for other sources.

On the other hand, Mars could not be made habitable without first being stocked with air and water; and such an undertaking seemed impossible. There was nothing for it, then, but to attack Venus. The polar surfaces of that planet, shielded by impenetrable depths of cloud, proved after all not unendurably hot. Subsequent generations might perhaps be modified so as to withstand even the sub-arctic and "temperate" climates. Oxygen was plentiful, but it was all tied up in chemical combination. Inevitably so, since oxygen combines very readily, and on Venus there was no vegetable life to exhale the free gas and replenish the ever-vanishing supply. It was necessary, then, to equip Venus with an appropriate vegetation, which in the course of ages should render the planet's atmosphere hospitable to man.